Wireless communication systems have been widely deployed to provide various types of communication services such as voice or data services. Generally, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmit power, etc.). Multiple access systems include, for example, a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, etc.
A radio access network (RAN) configuration has been changed such that various types of small cells such as a pico cell, a femto cell, etc. interact with a macro cell. The RAN configuration refers to a heterogeneous cell configuration or a hierarchical cell configuration in which small cells for low power/near field communication coexist in addition to an existing macro cell-based homogeneous network. The heterogeneous cell structure is used to enhance quality of experience (QoE) by providing a high data transmission rate to a last user.
In small cell enhancements for E-UTRA and E-UTRAN study item (SI) as one of 3rd generation partnership project (3GPP) standard scopes, research has been ongoing into enhancement of indoor/outdoor scenarios using low power nodes, and the scenarios is described in 3GPP TR 36.932.
Considering such a trend, as a large number of small cells will be deployed within a macro cell, final UEs (user equipments) may be physically located closer to a network. Accordingly, it is expected that communication will be performed through a UE-centered zone in a next generation radio access network, instead of the conventional physical cell-based communication. To realize communication through UE-centered zones with the aim of increasing throughput, technical issues for implementing a service-providing unit such as the UE-centered zone different from the current service-providing unit such as the physical cell should be drawn and handled.
In addition, the introduction of the small cell may significantly affect a current remote area network (RAN). Particularly, in case that a number of small cells are installed within a macro cell area, it may cause a problem that a UE matches synchronization with a small cell not associated with the corresponding UE or performs a procedure for accessing the non-associated small cell.